Knife



' Feb. 7, 1939. l. STERN ET AL KNIFE Filed June 25, 1935 8SheetsSheet l[ya/111,11 okolnl'lroff In) 117' Be J Vasquez r0 :IJJ. arnue'lOstrolen/r Filed June 25, 1935 8 Sheets-Sheet 2 LENGTH OF cu'r "L" 0 1 N[/5 N T036 96 (zap 6 ter- 11 u h Ben a mu! fikolnikof'f 5P5 ED RAT'O QJqu hffl10]. Pea ueira .5 amuel Ostra ehk F1 '7 W Z 2 ATTORNEY I Feb. 7,1939. Iv STERN ET AL 2,146,274

KNIFE Filed June 25, 1935 8 Sheets-Sheet 3 I N VE N T0735 .Qsaap filer/1Berg 2221101 'filrolrukaff uuenl-inaJ. Pea aelra %r L -$amuel Ostro enkBY 5 w j: @m

' ATTORNEY.

Feb. 7, 1939.' l. STERN ET AL 7 2,146,274

KNIFE Filed June 25, 1935 8 Sheets-Sheet 4 I N VE N T026 Osaka c: S h?r11 75 e n 'amin filrolni/raff' Ju ven 1,110]. Pesyuez ra SamuelO-sfratenk BY ATTORNEY.

Feb. 7, 1939. f LST-ERN Em 2,1 21

I KNTFF.

. Fi led June 25, 1955 s Sh ee t s-Sheet 5 Fig-12 "Hil M rm I I.INl/tT/VT'OPS 95aac Stern ATTORNEY.

Feb. 7, 1939. 1. STERN ET AL 2,146,274

/ KNIFE Filed June 25, 1935 a Sheets-Sheet 7 ATTORNEY.

Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE KNIFE Isaac Stern,Benjamin Skolnikofl', Juventino Joseph Pesquelra, and Samuel Ostrolenk,New

. York, N. Y., assignors to .S 8: S Corrugated Paper Machinery 00.,Inc., Brooklyn, N. Y, a corporation of New York Our invention relates tonovel apparatus for and methods of cutting fibrous paper boards and moreparticularly, relates ,to novel apparatus for and methods of operatingknives continuously for cutting varying lengths of fibrous boards.

predetermined lengths by the knives which are usually operated in acycle whose time varies in accordance with the size of cut desired.

The operation of the knives may be broadly divided into twoclassifications, one, the intermitgent operation and, two,'thecontinuous operaion.

In the case of the intermittent operation of the knives, eithenfiatimingdevice or a target is provided. The target is engaged by the endof the paper being'fed past the knife so that when a predeterminedlength of paper has been fed past the knives, the forward edge of thepaper engages the target which in turn operates to cause an engagementofa clutch-*through'which a driving shaft drives the drum carryingthe.knife.

The knife drum which up to this point has been stationary now starts itscycle of operation, rotating to a point where the knife engages and cutsthe paper and thereafter continues the rotation until the cuttingoperation has been completed and the drum with the knife thereonhasreturned to the original stop position at which point the clutchdisengages the drum from the driving shaft. A cycle has thus beencompleted and the drum is prepared for the second cycle whenthe new edgeof the strip material engages the target to again close the clutch.

In this type of operation, due consideration has to be given to the timefrom the instant when the edge of the paper engaged the target to thebeginning of the out which obviously takes place sometime later. In thisinterval, there is one variable whose time constant is not predictable,namely, the time from the instant when the clutch engages to connect thedriving and driven shaft to bring the drive shaft from a stationarycondition t"o full speed.v The clutch,because of the severe strain towhich it is subjected in bringing the driven shaft up to the drivingshaft speed soon begins to wear so that the time interval between theoperation of the target and the engagement of the knife with the papervaries depending upon theslip of the clutch. This results in an error inthe size of'the paper out of as much as a quarter so! an inch whichbecomes a very serious factor when a large number of cut sheet materialis involved, not only in the loss of paper 'Ihe second principlereferred to above involves a construction in which the drums carryingthe knives are rotated at a continuous speed and at a predeterminedposition in the cycle of the drum the knives engage the paper to performthe cut- .ting operation. t

For different size cuts, provision is made for changing the speed of theknife carrying drum either to a greater or lesser speed dependinguponwhether a smaller or larger cut size is. desired.

During the cutting interval, the knife engages the paper and accordinglymust move forwardly with the paper at the same rate of speed as thepaper, if it is to avoid either the tearing or buckling of the paperduring cutting. While this is a comparatively simple problem for a.single time cycle of the cutting knives, the problem is rendered morediiilcult where the cycle time is changed for different sized cuts.I-Ieretofore the only solutions proposed for obtaining a synchronous orequal rate of speed of movement of the knives and the paper at the, in-

stant of cutting have been based on principles involving complexmechanismand providing only an approximate synchronism.

Thus in the patent to Swift No. 917,503, no detailed solution for thisdifficulty is" suggested. In

the patent to Sieg No. 1,897,867, it "is .proposed .to

follow the principle outlinedin the patentvto Harbrecht, N0.-1,39,124 byusing elliptical-gears for driving the knife carrying drums. By reasonof these elliptical gear drives, the knife carrying drum isgraduallydncreased from a minimum speed at the beginning'of a cycle upto a speed at which the drum is rotating at the speed of the corrugatedpaper web. At this point the knife engages the paper for cuttingoperation. At the end of the cutting operation, the drum through theaction of the ellipticalgears again reduces its speed to the originalminimum speed.

vIn order to change the size of cuts, the time consumed for this cycleis changed as described However, both Harbrecht and Sieg make afundamental erroneous assumption. An elliptical gear, by definition-f isone whose speed is continuously changing, While it is possible to,obtain an approximation of uniform for cutting at one position of theelliptical gear'where it is most nearly circular so that the knives willmove at the same speed as the paper throughout the cutting period thisis not possible at a variety of positions of the elliptical gears.Accordingly, when either Harbrecht or Sieg shift the position of theknife with respect to the elliptical gears there results inevitably anon-synchronous condition between the speed of the paper and the speedof the knife at least during a portion of the cutting period.

Thus in both Sieg and Harbrecht, two adjustments are made, namely, onewhich involves a change in the time cycle of the knife and the otherinvolving a. compensation for this change in time cycle by a change inthe relative position of the knives and the elliptical gears, thedistinction between Harbrecht and Sieg being that in Harbrecht thecutting machine must be brought to a stop for adjusting the ellipticalgears with respect to the knives whereas in Sieg this can be done withthe machine in operation. In both cases, however, a fundamental fallacyin principle of operation exists.

In accordance with our invention, we contemplate a construction ofknives and the operation thereof in which no compensating adjustment ofthe elliptical gears is necessary or provided. The drum carrying knivesare in a fixed and rigid position with respect to the elliptical gearexactly as is obtained in Harbrecht before any adjustment thereof isattempted. The only adjustment is the time cycle adjustment as inHarbrecht, but no change in the relative positions of the drum withrespect to the knife is made; instead, as pointed out above, this ismaintained rigidly fixed so that that portion of the elliptical gearwhich is either accurately or approximately circular may be employed forthe cutting interval to maintain the knives moving in synchronism withthe speed of the paper.

This condition for every time cycle variation is obtained by merelyusing more or less of the elliptical gear for driving the knife drums.

In accordance with our invention, we drive the knife drums from twosources; first, from a Reeves directly through circular gears whose timeinterval is changed for obtaining different sized cuts. A second drivefor the knife drums is obtained through a pair of elliptical gears whichare normally non-operative while the cutting cycle is being determined.

At a predetermined point in the cycle, the elliptical gears becomeeffective to increase the speed of the knife drums to the cutting speedat which point the knives move at the same speed as the paper.Thereafter, the knives are decelerated by the elliptical gears untilthey reach thespeed at which the circular gears again drive the knifedrums for repeating the cycle.

Thus as will be more clear from the description to follow, we have madea radical departure both in the principle of operation and theconstruction. Instead of adjusting elliptical gears which requirescomplicated mechanism and in the end is inaccurate, we make noadjustment whatsoever on the elliptical gear adjustment but insteadprovide multiple drives, a principle never heretofore used in thismechanism. The multiple drive in which the function of the timing thecycle is assigned to one drive and the synchronizing to the other driveis far simpler than any other system requiring practically little or noadditional parts. At the same time, it is far more accurate inoperation.

Accordingly, an object of our invention is to provide a novelconstruction of knives for strip material in which two separate drivesin parallel relation to each other are provided for the knife drums, onedrive determining the time cycle and the other for bringing the knife tothe synchronous speed.

Still another object of our invention is to provide knife drums forcontinuous strip material in which a fixed relation is maintainedbetween the knife drum and the elliptical gears.

Still a further object of our invention is to provide novel apparatusfor and methods of cutting strip material in which it is necessary tochange the time cycle only and noncompensating adjustments of ellipticalgears are required.

There are other objects of our invention which together with theforegoing will appear in the detailed description which'is to follow inconnection with the drawings.

Figure l is a schematic illustration of our invention.

Figure 2 is a detail of a clutch used in our novel device.

Figures 3 to 5 are illustrations of several positions of ellipticalgears used in our invention.

Figure 6 is a graph of the angular speeds of the cutting knives plottedagainst their angular displacements.

Figure 7 is a speed ratio-sheet length curve.

Figure 8 illustrates our invention employing an intermediate ellipticalgear.

Figure 9 is a side elevation view of the machine.

Figure 10 is the discharge end view of the machine in elevation.

Figure 11 is a sectional view on '04 I l-li of Figure 10.

Figure 12 is a sectional view on line i2--l2 of Figure 10.

Figure 13 is a sectional view substantially taken on line l3-l3 ofFigure 10.

Figure 14 is a sectional view showing a modified form of the gearmechanism.

Figure 15 is a sectional view of the measuring scale mechanism.

Figure 16 is a sectional view of a modified form of the mounting of thecutting knives.

Figure 17 is a schematic illustration of a modifled form of ourinvention.

Figure 18 is a schematic illustration of a further modified form of ourinvention.

Referring now more specifically to Figure l, rotating power applied tothe shaft I l rotates the Reeves drive l2 of well-known constructionwhich we have here illustrated schematically by the cone l3 secured forrotation on the shaft II and the'cone ll connected to the cone l3 by thechain I5. In the manner well-known in the art, by shifting the chain ISin a transverse direction from its direction of rotation, the speed ofthe cone It may be varied any desired amount within predeterminedlimits. Cone H is mounted on and drives the shaft l6 which in turncarries the one-way clutch ll of well-known construction. This clutch isschematically illustrated in Figure 2 and comprises a driver disk I8mounted on and driven by the shaft l6 and an outer rim is mounted on androtatable with shaft 2|. The driver disk I8 has a series of camindentations 23 around its periphery in which there are seated theindividual'rollers 22., As is well-known in the art, so long as the rateof rotation of the driver disk I8 is less than the rate of rotation ofrim IS, the rollers 22 will tend to remain in the position shown. Thus,no rotating energy can be transmitted from the rim I! to driver l8.

when, however, the driver 18 tends to rotate faster than the rim II, therollers 22 are forced into the smaller portion of the cam as, forexample, portion 23, thus providing a gripping action between the drivendisk I8 and the rim l9 and a driving power is thus transmitted from thedriver I8 to the rim l3, maintaining the rim in synchronous rotationwith the driver. It will thus be clear that the rim l9, while it may attimes rotate at a faster speed than the driver l8, cannot rotate at alower speed. The importance of this will be clear from the descriptionwhich is to follow.

Mounted on and rotatable with the shaft 2| is a pinion 24 meshing with aspeed reduction gear 25 which is mounted on the shaft 26 of the knifedrum 21, carrying the knife blade 28. Gear 25 in turn meshes with thegear 3| mounted on shaft 32, carrying the knife drum 33 on which ismounted the knife 34 which incooperation with the knife 28 functions tocut the web material 35 in varying lengths in a manner to be described.

The operation of the power transmission described in the above will beobvious. Power normally supplied from the power shaft H is transmittedthrough the Reeves drive |2 to the shaft' 5 and thence through theclutch |1, shaft 2|, gears 24 and 25, to the knife drums 21 and 33. Inorder to obtain different sized cuts it is merely necessary to changethe rate of rotation of drums 21 and 33 by shifting the chain l5 of theReeves drive to vary the rate ofrotation of the cone l4 with respect tocone l3.

However, as will be recalled, from the descrip tion above this alonewill not sufflce since at any change in speed of drums 21 and 33 theknives 28 and 34 will not move at the same speed as the web 35 andaccordingly there will result either a tearing or a buckling of thepaper.

To correct for this, we do not drive the drums 21 and 33 throughout thecycle from the power transmission described above but instead provide amultiple or by-pass drive which functions in cooperation with the firstmentioned drive to bring the knives to the proper speed relation withrespect to the web after the timing of the cycle has been previouslydetermined by the first drive.

Thus, power shaft I also carries meshing gears 36 and 31 the latter geardriving the shaft 38 carrying the feed rolls 39 which feed the web 35 ata! speed equal to the speed of the corrugating machine through a directmechanical connection thereto from the power shaft l in a mannerwellknownin the art.

Also mounted on the power shaft II is a second clutch 4| similar inconstruction to the,clutch of Figure 2 and whose driver equivalent tothe driver I8, is mounted on and driven by the power shaft In theposition shown, the knives 28 and 34 have just come into engagement atthe point 48 preparatory for a cutting period in the cycle. At thisposition, it will be noted, the elliptical gears 46 and 41 are in theposition at which maximum speed ratio is obtained. Assuming that at thisposition the speed ratio is one to four obtained by suitable design ofthese elliptical gearathen the gear 41 is rotating at four times thespeed of elliptical gear 46 whose speed in turn is determined by therotation of power shaft I In accordance with our invention, this speedincrease in the gear 41 which is transmitted through gears 3| and 25 topinion 24 and thence to shaft 2| causes the shaft 2| to rotate at aspeed which is higher than the maximum speed which can be obtained onshaft |6 for the smallest sized cuts desired.

As a result, inasmuch as clutch I1 is a one way clutch, the shaft 2|will rotate from power supply to shaft through the power transmissionincluding the elliptical gears 46 and 41 at a greater speed than andfree from shaft l6.

Accordingly, during the cutting period, the

knife carrying drums 33 and 21 are. driven from the power supplyJlthrough clutch 4|, gears 43 and 44 and elliptical gears 46 and 41.Thespeed of rotation is a predetermined and fixed value determinedsolely by the gear trains in this latter power transmission system andspecifically by the relative position of the elliptical gears 46 and 41.Inasmuch as the cutting position is definitely fixed with respect tothese elliptical gears, they can be cut over the cutting are so thatthey are substantially circular and therefore provide power for theknife drums at a constant speed during cutting. Moreover, in view of thefixed relation between the elliptical gears and the knives, the angle ofcut may be made as large as desired over a substantial are, limitedsolely by the range of cutting sizes desired in a manner which will beclear from the description to follow. It is only necessary that whatevercutting angle is employed, the corresponding portion of the ellipticalgears shall be made, substantially circular.

At the end of the cutting period, that is, when the opposite edges ofthe knives such as at 46 come into contact, the elliptical gears enterinto a position at which the speed ratio begins to change the gear 41gradually decreasing its rate of rotation with respect to the gear 46 asthe speed ratio therebetween gradually reduces from the one to fourratio to a one to one ratio and then finally to a. four to one ratio atwhich the gears 46 and 41 are in a diametrically opposite position fromthat shown.

As the .speed of shaft 32 decreases with the gear 41, the powertransmitted through gears 3| and 25, pinion 24, to shaft 2| willgradually reduce the speed of rotation of the shaft 2| until itapproaches the rated rotation of shaft l6. As the speed reduction nowcontinues, the instant the shaft 2| tends to rotate at a lower speedthan shaft |6,,the rollers 22 will promptly engage in the mannerdescribed above and power will now be transmitted from shaft |6 throughclutch l1, shaft 2|, pinion 24 to gears 25 and 3| thus driving the knifedrums 21 and 33 at a rate determined by the Reeves drive l2. Power istransmitted, now, back over shaft 32 through elliptical gears 41 and 46,shaft 45 and gears 44 and 43 to the shaft 42 which in turn carries theone-way clutch described above. Since at this portion of thecyclethe'elliptical gears 41 and 46 are in reverse position from thatoriginally described, the elliptical gear 46 will rotate at four timesthe speed of elliptical gear 41 and therefor transmit driving power tothe shaft 42 which drives the latter at a greater speed than the powershaft ll. Accordingly, shaft 42 rotates free of power shaft During thisentire period, the speed of the knife drums is determined solely bytheReeves drive.

As the rotation continues, the ratio between the elliptical gears 41 and46 again undergoes a change back to the original value passing from theratio of four to one between gears 41 and 46 respectively through one toone ratio and then slowly back to the one to four ratio between gears 46and 41 respectively.

During this change, shaft 42 gradually decreases in speed until itapproaches and finally arrives at the speed of power shaft ll. At theinstant it tends to go below the speed of shaft clutch 4| becomesoperative to again drive the shaft 42. At this instant the speed ratiobetween elliptical gears 46 and 41 is such as to raise the speed ofshaft 2| slightly above the speed of shaft I6 and the shaft 2| is againfree of the latter shaft. During this next interval as power is nowsupplied from power shaft through clutch 4| and elliptical gears 46 and41, the knife drums are gradually accelerated up to the cutting positionat which point cutting again begins and a second cycle of the typedescribed above is repeated.

Summarizing the above, it will now be seen that a complete cycle may bedivided into four distinct intervals. There is first the interval ofcutting during which the drums are driven from the power supply throughclutch 4| and to elliptical gears 46 and 41. At a predetermined positionof these elliptical gears at which they are cut circular, the secondinterval follows in which the speed of the drums is graduallydecelerated as the elliptical gears change their speed ratio until thedrum reaches its minimum speed at which time the drive is switched fromthe above described transmission to the Reeves drive l2, clutch l1,shaft 2| and pinion 24. This is the third interval. The latter drive maybe varied under control of the Reeves drive in the well-known manner forchanging the time of each cycle in order to change the size of cuts. Thefourth interval is the period when the power is switched back from theReeves drive to the first mentioned transmission during which the drumsare accelerated to bring the knives to the speed of the web. Inasmuch asthe first, second and fourth intervals are of fixed value andunchangeable the time interval therefore can be predetermined, andaccordingly by a proper change in the rate of rotation in the thirdinterval through adjustments of the Reeves drive, the complete timeinterval in each cycle can be predetermined for obtaining diflerentsized cuts of material.

The importance of this arrangement resides in the fact thatfor allchanges in the Reeves drive, no change whatsoever is necessary in theelliptical gears and these remain fixed with respect to the knives thusinsuring invariable synchronous movement of the knife with respect tothe web.

It will now be clear that the knives are driven alternately by theclutches l1 and 4| respectively in such a manner that when one clutch isdriving, the other is free. The source of rotation of the knives will infact be the faster of the two that may be communicated to them by eitherclutch.

Clutch H which obtains its power through the variable speed Reevesdrive, tends to operate the knives at a constant rate while clutch 4|which itself rotates uniformly and is independent of the variable speeddrive, tends to operate the knives over a drive in multiple with thefirst drive through a cycle of varying speed. The pair of ellipticalgears interposed between it and the knives controls the cutting periodto within a small portion of the maximum of this varying speed.

This maximum speed is attained when the pair of elliptical gears is inthe position shown in Figure 3. Here gear 41 is, of course, rotatingmz/mi as fast as gear 44, and it is in the neighborhood of this instantthat the knives engage the moving paper web material, the differentelements being so proportioned as to make the horizontal component ofthe linear speed of the knives equal to the speed of the material, orvery nearly so.

As the elliptical gears are displaced through certain angles, as shownin'Figure 4, gear 41 will slow down with respect to gear 46, since theactive radius 11 of gear 41 has increased, and the active radius 7':ofgear 46 has decreased. The angular speed of gear 41 relative to thatof gear 46 will thus go on decreasing until it reaches a minimum, whichoccurs when both members of the pair have turned through an angle 1rwith respect to the position in Figure 3, as shown in Figure 5. Heregear 41 will then be rotating mi/mz as fast as gear 46. In general, gear41 rotates 1'2/1'1 as fast as gear 46, n and r2 varying, of course, withthe angular displacements a1 and an of the respective members.

Clutch 4| has a tendency to rotate gear 46 at a uniform angular speedand, consequently, in the absence of clutch l1, gear 46 would alwaysrotate at a constant angular speed, say (92 and owing to the ellipticalshape of the members, it would drive gear 41 at a varying angular speedwi=W2, where On the other hand, clutch I1 has a tendency to rotate gear41 at the constant angular speed w1=W1 and would do so in the absence ofclutch 42 through a complete cycle. Therefore, when clutch I1 isdriving, gear 41 has the angular speed w1=W1, constant. It will be seen,then, that gear 41 and therefore the knives 28 and 34 will be driveneither at the angular speed W1 or at the angular speed W2, depending onwhich is the greater.

During a complete cycle, W: would vary from the maximum (ma/mm: to theminimum (mi/mama, while W1 would remain constant. Itis clear then thatif m m a 1 z there will be in general two instants in the whole cycle inwhich the two possible angular speeds W1 and W: are equal. It is atthese instants that the burden is passed from one clutch to the otherwithout interrupting the march of the machine. W1 may be varied at willto suit requirements through the variable-speed Reeves drive l2 asdescribed above, but this variation must lie within the extremes of theinequality above. Hence.

In: W, maximum w;

i W; minimum -w;

whence angular speed 101 of E1 plotted against the. angulardisplacements m1 of the same gear. Here it will be seen that the twopossible values W1 and W: of 1111 are equal at the points ofintersection F1. F2 of the two curves, these points having abscissas011:0, a1, a1" 101 must be the greater of the two possible speeds W1andW2 and therefore M will be variable in the intervals :1:0 to a1, 0:1" toai' etc., and constant in the intervals 1x1 to on", 111' to a1"" etc. Inother words, clutch 4| drives in the intervals 0 to a1, on" to 111"etc., at a varying angular speed, and clutch I1 drives in the intervals:11 to 0:1", ou' to a1"" etc., at constant speed. The points (11', a1"are, of course, the roots of the equation W1=Wz, that is, of theequation The knives engage the material at their maximum angular speedor within a small neighborhood of it, that is, when w1=Wz maximum.Hence, it w: and R1 are the angularspeed and radius of the feedingroller, and Re the distance from the axis ofrotation of either knife tothe material (the "radius of the knives), we .ve

RcWz maximum=Rywl that is, since Since gear 41 rotates through an angle21r (one revolution) for every cut made, and since angular speeds areproportional to angular displacements 1L2: co 6 where 6 is the angulardisplacement of the feeding roller per cut made. Now, if L is the lengthof the pieces of material being cut, we have cz1"=21ra1', and, forreasons of symmetry, the last equation may be written in the form L "QM1 W2 m l Equation (1) may be written vHence 2 tan ia 1 A+ since A=-B.=1, as may be easily verified.

W1 is constant, and therefore Hence This last quation indicates thecorrespondence between the values of W1 and L, and therefore makespossible the calibration of the variable-' speed drive for the differentHe desired. Thus, assuming an arbitrary value for W1, a1 is obtainedfrom Equation (A), and from Equation (5) is obtained the correspondingvalue of L. An accurate graph (or table) may then be made, givingcalculated values of L against assumed values of W1.

Assuming that it is required to cut sheets varying in such lengths thatthe longest is N times the shortest, from (3') it will be seen that Theshortest sheet is cut when 171 is the fastest, that is, when HenceTherefore, since L maximum/L minimum=N,

and the pair of elliptical gears may now be proportioned by giving m ormm a suitable arbitrary value. For instance, if L maximum=120" and Lminimum=30", we get N=4=. If we make m1=4", we get m2=16", and the majoraxis of the ellipses will be 2a=mi+ma=20". The minor axis will be 2b=2-y/a' }(m m 16' the latus rectum 2p 2= 1 2.8 and the eccentricity Tofind the capacity of the variable-speed drive Equation (a) may now bewritten W max.=Nu,

W1 min.-%

Hence W1 maximum/W1 minimum=lv and if the lengths of cut range from 30"to 120", for which N=4, the above ratio becomes 16. Therefore,in thisexample,the variable-speed drive may be chosen as having a range ofspeed ratios of 1:1 to 1:16, or 2:1 to 1:8, or'4:l to 1:4, etc.

Assuming that the drive is required to cut' pieces of from 30" to 120"in length, then by (6), N=120/30=m /m =4 If m1=4", mr=l6", the otherelements of the elliptical gears will be as determined. Putting Rt=Rc in(2) for the ratio of the angular speed of the feeding roller to that ofgear 4'. From (5") 120= 2112;)(4 that is for the radius of the fedingroller. Also R=4.7'75", since R4 and Re are assumed to be equal in thisexample. Let P1, P2, G1, G2, Ga, G4 stand for the diameter (or number ofteeth) of gears 24, 43, 3i, 2!, 30 and 31 respectively in Figure 1. Thenand if Ga=G4, G1/P2=4. Let us be the angular speed of cone i4 of thevariable speed drive, and we that of cone ii. The capacity or thevariable speed drive is N=16. Now, if a drive having a range or speedratios oi from 4:1 to 1:4

is chosen, then 66 01 max. 4:0 40 And similarly,

m min.=w

since G:=G4.

From Equation (2) 60 W maximum 4w;

W minimum {on M Hence be the speed ratio of the variable speed drive towhich it is to be set for cutting a piece of length L. Since G1 (0 4 itfollows that or, if on is given in degrees,

2 tan ion) 180a l L [2 tan 4 Q With the values for p(=6.4") and (=0.6)already known the second of Equations (A) will become cos a 0.5333Q-1.1333 (8) Equations (7) and (8) are the expressions that were to beround to calibrate the variable speed drive. A graph of Equation (7) isgiven in Figure 7.

With so high a value as 4 for mz/mi, the elliptical gears may appear tobe too elongated. It is possible to interpose between gears 46 and 41another elliptical gear, thereby reducing the eccentricity of theellipses. An arrangement of a system of three elliptical gears is shownin Figure 8 in the position for the maximum angular speed of 41. It isclear here that the maximum angular speed of 41 will be The motion of 41in general is W,=w (A +B cos a) the minimum where Equation (9) abovetakes the place of (1) in the above. Equation (a) will now become 1 In;W

1 max w,

whereas the second 01' Equations (A) will now 1 W cos a i) Equation (2)will change into R 2 w2'-="R i (o (10) and Equation will undergo aslight change in L=2R w [:2 tan l In deriving Equation (11) it is foundthat A1 B1 =1, as was the case with similar symbols in the derivation ofEquation (5). Equations (5) and (6) will-now become Lmin.=21rR;

whereas Equation (5") remains the same:

L max.=21rR r All equations in the above not involving the ratio mi/mzwill remain unchanged, and those involving this ratio will remainunchanged but for the expression (mi/m2) which is to be inserted inplace of mi/mz.

Let L minimum=30", L maximum=120". Then, from Equations (12') and (14) LmaximumL minimum=4=(mz/mi) Hence Making m1=4", the proportion of theelliptical gears becomes m2=8", 2a=12, 2b=l1.314", 22J=10.667",e=0.333.Followingthesamestepsassume R;=Rc=15/1r=4.775", G4/G3==2, P1/G1= /2,range of variable speed drive: 4:1 to 1:4, calibration of drive: asgiven by Equations (7) and Equations (1) and (9) were derived from thepolar equation of the ellipse, the well-known properties of the figure,and the fact that angular speeds are inversely proportional to activeradii. Angles and angular speeds are supposed to be in radians andradians per second, respectively, in the above discussion in order tofacilitate the analysis.

In the above, the invention has been described in connection with aschematic illustration of the invention. In the following the inventionis described with specific reference to a construction.

Referring to Figure 11, the web to be out,

'is travelling between the feeding. rollers 5|, 52

at a uniform speed, towards the cutting knives 28, 34 which are mountedon drums 21 and 33 respectively. Drums 21 and 33, are, in turn, mountedon shafts 53 and 54. The knives shafts are geared to each other torevolve in opposite directions by equal spurs 25 and 3|, also rigidlymounted on shafts 53 and 54 respectively, Figure 12. The knives receivetheir power either from shaft |6 or shaft 42 depending on certainconditions as described above. Shaft l6 forms parts of the driven memberof a variable speed transmission |2, such as Reeves transmission, uponone of whose ends the inner or driving part 1 I8 is rigidly mounted. Theouter or driven'part I9 is keyed to shaft 2| in line with shaft l6 andis driven by outer member If! whenever its speed of rotation is notgreater than the speed of rotation of part l8, due to the wedging effectof rollers 22 as is well known in the art. Shaft 2| carries spur gear 24which meshes with and at times drives spur gear 25 which is keyed toshaft 54.

Shaft is part of the driving member |3 of the variable speedtransmission and carries on one end the inner or driving part, a clutch4| similar in construction to clutch Driven part 6| of this clutch iskeyed to shaft 42 onto which spur gear 43 is rigidly mounted. Spur gear43 cooperates with spur gear 44 through idler 62. Spur gear 44 is keyedto shaft 45 to which is also keyed member 46 of a pair of ellipticalgears, the other member 41 being keyed to shaft 54. Clutch 4| drivesshaft 42. as in the first clutch 25 whenever the angular speed of shaft42 is not greater than the angular speed of shaft The whole train ofgears described above is enclosed in box 63 which also forms the bearingsupport of the different shafts of said gears. The

opposite ends of shaft 53 and 54 are borne by bearings forming part ofopposite support 64. For safety purposes, the revolving knives maybeenclosed in hoods.

Shaft II is extended to go through support 64 to the outside where it isprovided with means to receive power such as the helical gear 65, whichengages helical gear 66 mounted on driving shaft 61' Upper feedingroller 5| is positively related to shaft II by any well known means. Inthe drawings, the driving of this feeding roller is accomplished bymeans of helical gear 68 engaging helical gear 55 and is keyed to lowerend of vertical shaft 69. To the upper end of 69 is keyed helical gear10 which meshes with helical gear 1| driving thus shaft 12 on which Handfeeding roller 5| are rigidly mounted. In cases where this kind ofcut-off mechanism is used immediately at the discharge end of themachine manufacturing the web to be cut, the feeding rollers above maybe dispensed with. However, the cut-off mechanism should then bepositively related to the machine producing the web in order to assuresynchronism.

The speed ratio of the variable speed transmission may be adjusted andmeasured by turning the hand wheel I3. As shown in Figure 15, pinion I4is mounted on shaft 15 to which wheel 13 is keyed, and meshes with largespur -76 on which a scale 11 conveniently graduated is placed androtates therewith, the reading being indicated by the stationary pointer18, (Figure 9,).

In the absence of clutch H, the angular speed of the knives would beentirely variable throughout a complete revolution, due to theinterposition of the pair of elliptical gears between the knives shaft54 and the driving shaft IL This variable speed is graphicallyillustrated by the sinusoidal curve in Figure 6, plotted against theangular displacements of the knives. On the other hand, in the absence,of clutch 4|, the

angular speed of the knives would be constant with respect to theangular displacements of the knives throughout a complete revolution.

This constant speed is shown in Figure 6 as represented. by thehorizontal line 11-41. If, however, both clutches are present, theangular speeds of the knives will be variable in some intervals of thecycle, and constant in others. This is shown by the heavyv solid curvein Figure 6, which is composed of portions of the variable and constantspeeds that the knives may partake of, joined at the points P1, P2,where the variable speed equals the constant speed.

The variable speed transmission may be adjusted to increase or decreasethe angular speed of the knives in the intervals of constant speedswithin the minimum indicated by the horizontal line (lo-a'o and themaximum indicated by the horizontal line a'1a1 (Figure 6), which gothrough the minimum and maximum points of the sinusoidal curve,respectively. The cutting knives are so located angularly that thecutting is made at the points of maximum angular speeds, whereas thesweeping radius of these knives is so determined that their linearspeeds substantiaily correspond to the speed of the travelling web atthe time of cutting.

Scale 11 (Figure 15) may be graduated to read lengths of cuts directly.

Since the eccentricity of the ellipses in a pair of elliptical gearsincreases with the ratio of the maximum to the minimum speeds of thefollower, when a large ratio is desired in order to obtain a wide rangeof cuts, the gears may be too elongated for good performance. Theobliquity of the resultant force on the teeth would be in this case toopronounced, and there would be a strong tendency in some portions of therim to throw the teeth out of mesh. In order to reduce the eccentricityof the gears, a train of three or more elliptical gears may be used thatwill give the same kinematical results as in the case of two ellipticalgears.

Figure 14 shows the application to the invention of a train of threeelliptical gears 82, 83 and 84. Here spur gears 88, 81 and 88 have thesame function as the corresponding gears of Figure 12. The idler,however, is absent.

The description of the cut-off mechanism above was made in connectionwith a revolving type of knives. Several other types may also be used.In Figure 16, I have shown a knife consisting of cutting edges 9I and92, mounted on the front members 93 and 94 of frames 95 and 96 which arehinged at 81 and carried around on the drops of the cranks 98 and 99 asthey revolve in opposite directions. The hinges 91 oscillatehorizontally while the cutting edges travel in very nearly circularpaths keeping themselves substantially in vertical position during theirmotion. Frames 95 and 98 are self-supporting. It will be understood thatthe cranks II and 12 are driven by the mechanism described above fordriving the knife drums so that the time cycle may be varied but thecranks at instant when the knife edges are cutting the paper, move insynchronism with the paper.

In Figure 17 I have illustrated a modified form of my invention in whichI have eliminated the clutch mechanism l1 and H of Figure 1. The samedrive and speed control through the Reeves is obtained as in theprevious modification. Secured to shaft I8, however, and rotatabletherewith is a mutilated gear I03 which has teeth only about a portionof the circumference, this portion being that part of each cycle duringwhich the knives 28 and 34 are to be driven at a predetermined speed inaccordance with the size of cuts to be made. In the multiple driveconnection, shaft II is connected through the pulleys I00 and IM fordriving gear I02 meshing with the mutilated gear I03. Gear I03 like gearI03 has teeth about only a portion of its circumference, namelyv thatportion in the cycle during which the knives 28 and 34 are to beaccelerated and decelerated from a speed below cutting speed up to thecutting speed and then back to the original speed.

In normal operation, the gear I03 meshing with the drum gear I04 willdrive the knives 28 and 34 at a predetermined speed determined by theReeves drive I2. This rate of speed during the 'period while gear I03meshes with gear I04 determines the size of the cut sheets. A thirdmutilated gear I03 meshing with gear I04 provides a third multiple drivefor the knives 34 and 28.

In operation, at the beginning of the cycle gear I03 drives the knivesas described above during that portion of the cycle when the speed ofthe drum is maintained constant and determined by the Reeves drive I2 asexplained above. At the end of this interval, the teeth of gear I03 areabout to disengage from the teeth of gear I04. At the instant that thelast tooth of gear I03 passes from engagement with gear I04, the firsttooth of gear I03 which up to this point has been driven .through thegear chain including the elliptical gears, engages with the tooth ofgear I02.

From this point on in the cycle, driving power is supplied through gearsI02, I03 and the ellipticalgears I01 and I08. As the gears rotate, thegear ratio between the gears I01 and I08 gradually undergo a change inthe manner described in detail above as the small part of gear I01meshes with the large part of gear I08 until a one to four ratio isobtained. At this time the knives 34 and 28 are rotating at theirmaximum speed at which point they are rotating at approximately thespeed of the paper.

Just before the knives engage the paper for cutting, gear I03 for a sortinterval disengages from gear I02 while gear I03 meshes with gear I04.During this latter interval, while these circular gears are in mesh, theknives start their cutting operation. During this period, the knives arebeing driven by the circular gears and at a fixed and invariable speedwhich is always the same as the speed of the paper.

At the end of the cutting interval, gear I03 disengages gear I04 whilegear I03 again meshes with gear I02 and as the elliptical gears continueto rotate, the gear ratio between gears I01 and I08 gradually undergoesa change until knives 34 are again rotating at their minimum speed. Atthis speed the first tooth of gear I03 again meshes with a tooth of gearI04 to repeat the above described cycle.

Inasmuch as the speeds of gears I03, I03 and I03 are predictable, theirteeth may be so cut that they will invariably properly mesh with theircorresponding gears as they come into meshing contact. However, werecognize that this may create a problem and that there are, therefore,certain advantages in employing the power trans mission systemsutilizing the clutch described in our first modification.

To overcome the problem of these gear structures, we have provided afurther modification shown in Figure 18, in which the mutilated gear I09driven through the Reeves drive II, in turn d vives the gears whichdrive the knives 28 and 3 During the interval while the teeth of gearI09 are in meshing relation with their corresponding gear teeth, theknives 28 and 34 are driven at a constant speed which determines thesize of the cuts of the material. Although this is the minimum speed ofthe knives 28 and 34, the gear ratio between the gears H0 and III issuch that the shaft II2 rotates at a faster speed than the driver ofclutch 4I. Accordingly, clutch 4I rides freely and does not transmit anydriving power.

When, however, the last tooth of gear I09 passes from engagement withthe tooth of the gear driving the knife 28, the driver of clutch 4Ibecomes effective and drives the elliptical gears III and H2. Duringthis portion of the cycle,

the gear ratio between gears III and II 2 increases in the mannerdescribed above, accelerating the knives until they reach the speed of ithe paper. During this interval the knives engage and begin to cut thepaper. As in the previous case, the elliptical gears are made as armorsl 9 nearly as possible circular so that during the cutting interval, theknives are operated at a constant speed equal to the speed of the paper.

At the end of the cutting interval and as the drums continue to rotate,they are decelerated due to-the reverse changein'speed ratio ofelliptical gears Hi and H2.

When the drums have been decelerated to the original speed, the firsttooth of gear I09 meshes with the tooth of the drum gear and the abovedescribed cycle is repeated. In this case, inasmuch as the time intervalfrom the instant when the last tooth of gear I09 passes out ofengagement with the drum gear to the instant when the first tooth againengages is a constant and predictableinterval, the gear teeth of gearI09 can be designed so that they will always mesh with the drum" gearalthough in this casealso the first modification is found preferablebecause of simpler design problems.

Although we have not shown or described any of the details of the knifeconstruction, it will be obvious that we may use any of the well-knownarrangements of knives. It will be clear to those skilled in theart thatthe drums carrying the knives are mounted at a slight angle with respectto the direction of movement 01' the paper so as to produce straightcuts and that the knives specifically asapplied to knives forcut'tingcor- 'rugated board, it will be clear that it may be applied to knivesfor cutting any other material which is being fed at a continuous rateor whereever synchronism during a period of a variable cycle is desiredbetween two members.

The inventive concept resides as will now be clear dividing the time ofa cycle into four distinct periods, one, the period when synchronism isdesired; two, the decelerating period, three, the period which'controlsthe time of the cycle, and

four, the accelerating period and in so arranging the mechanism forcarrying this out, such as the elliptical gear here used for purposes ofillustra tion, that the only variable is the mechanism which controlsthe time of the cycle in the third period so that no changes of any kindare necessary in the elliptical gears or their equivalent.

By thus providing only one adjustment, the

, accelerating period, the decelerating period and what is of greatestimportance, the cutting period, all remain ata fixed value consuming aninvariable fixed interval of time.

Not only arev we thus able. to provide more accurate cuts than haveheretofore been possible, but our mechanism is greatly simplified and ismade relatively inexpensive.

In illustrating our invention, we have not shown any of the details ofthe corrugators but have merely schematically illustrated feed rollswhich determine the speed of the paper being fed to the knives and withwhich speed the knives must be maintained in synchronism during cutting.This speed is determined by driving the speed rolls from the same sourceof power described above, which drives the knives.

We claim:

1. In a device for cutting strip material, knife cutting means; meansfor feeding the strip matematerial.

rial to be out at a constant speed past the knife cutting means; meansfor continuously operating said knife cutting means in cycles to engageand out the strip material periodically; the cycle of the knife cuttingmeans comprising an interval during which the knife is operated at aconstant speed, an interval during which the knife cutting means isaccelerated to a speed synchronous with the speed of the strip material,a cutting interval during which the knife cutting means is operatedcontinuously and in synchronous speed with the stripmaterial, and aninterval during which'thev knife cutting means is decelerated to thefirst mentioned constant speed; and means for varying the speed duringsaid constant speed interval for varying the length of cuts of saidstrip 2. In a device for cutting strip materiahknife cutting means; asource of power for operating said knife cutting means; two multiplepower transmitting paths from said source of power to said knife cuttingmeans; a'one way clutch in each path; and means for selectivelyoperating said clutches for transmitting power selectively over eitherof said paths.

3. In a device for cutting, strip material, knife cutting means; asource of power for operating said knife cutting means; .two multiplepower transmitting paths from said source of power to said .knifecutting means; a one way clutch in each path; means for selectivelyoperating said clutches for transmitting power selectively over eitherof said paths; means whereby said knife cutting means are operated at aconstant speed over one of saidpaths; and means for adjusting the speedof operation over said path for varying the length of cuts of said stripmaterial.

4. In a device forcutting strip material, knife cutting means; means forfeeding the strip material to be cut at a constant speed past the knifecutting means; means for continuously operating said knife cutting.means in cycles to engage and cut the strip material periodically; thecycle of the knife cutting means comprisingan interval duringwhich theknife is operated at a constant speed, an interval durin knife cuttingmeans is accelerate to a speed synchronous with the speed of the sripmaterial, a cutting interval during which the :knife cutting means isoperated continuously and in syn.- chronous speed with the stripmaterial, and an interval during which the knife cutting means isdecelerated to the first mentioned constant speed; and means for varyingthe interval of said constant speed for varying the length of cuts ofsaid strip material.

cutting interval during-which the knife cuttingmeans is operatedcontinuously and in synchronous speed with the strip material, and aninterval during which the knife cutting means is decelerated to thefirst mentionedcon'stant speed;

and means for varying the speed and interval of said constant speedinterval for varying the length of cuts of said strip aterial.

which the 6. In a device for cutting strip material, knife cuttingmeans; means for feeding the strip material to be cut at a constantspeed past the knife strip material, and an interval during which theknife cutting means is decelerated to the first mentioned constant speedmeans for varying the speed and interval of said constant speed intervalfor varying the length of cuts of said strip material; and calibratedmeans for indicating the change in speed of said constant speed intervalnecessary for difi'erent sized cuts.

' 7. In a device for cutting strip material, knife cutting means; asource of power; a first and second multiple power transmitting pathfrom said source of power to said knife cutting means; means fortransmitting power from said source of power to said knife cutting meansover said first path for operating said knife cutting means at aconstant speed; and means in said second path for transmitting powerfrom said source of power to said knife cutting means for acceleratingand decelerating said knife cutting means from and to said constantspeed.

8. In a device for cutting strip material, knife cutting means; a sourceof power; a first and second multiple power transmitting path from saidsource of power to said knife cutting means; means for transmittingpower from said source of power to said knife cutting means over saidfirst path for operating said knife cutting means at a constant speed;means in said second path for transmitting power from said source ofpower to said knife cutting means for accelerating and decelerating saidknife cutting means from and to said constant speed; and means in saidfirst path for varying said constant speed at which the knife cuttingmeans is operated from said source of power.

9. In a device for cutting strip material, knife cutting means; asource'of power for driving said strip material at a constant speed pastsaid knife cutting means; a first and second multiple power transmittingpath from said source of power to said knife cutting means; means fortransmitting power from said source of power to said knife cutting meansover said first path for operating said knife cutting means at aconstant speed; means in said second path for transmitting power fromsaid source of power to said knife cutting means for accelerating saidknife cutting means to the speed of said strip material and deceleratingsaid knife cutting means to said constant speed; and means in said firstpath for varying said constant speed at which the knife cutting means isoperated from said source of power.

10. In a device for cutting strip material, knife cutting means; asource of power for driving said strip material at a constant speed pastsaid knife cutting means; a first and second multiple power transmittingpath from said source of power to said knife cutting means; means fortransmitting power from said source of power to said knife cutting meansover said first path for operating said knife cutting means at aconstant speed; means in said second path for transmitting power fromsaid source of power to said knife cutting means for accelerating saidknife cutting means to a speed synchronous with the speed of said stripmaterial at the instant of cutting said strip material and fordecelerating. said knife cutting means to said constant speed; and meansin said first path for varying said constant speed at which the knifecutting means is operated from said source of power.

11. In a device for cutting strip material, knife cutting means; asource; of, power for driving said strip material at a constant speedpast said knife cutting means; a first and second multiple powertransmitting path from said source of power to said knife cutting means;means for transmitting power from said source of power to said knifecutting means over said first path for operating said knife cuttingmeans at a constant speed; means including elliptical gears in saidsecond path for transmitting power from said source of power to saidknife cutting means for accelerating said knife cutting means to a speedsynchronous with the speed of said strip material at the instant ofcutting said strip material and for decelerating said knife cuttingmeans to said constant speed; and means in said first path for varyingsaid constant speed at which the knife cutting means is operated fromsaid source of power.

12. In a device for cutting strip material, knife cutting means; asource of power for driving said strip material at a constant speed pastsaid knife cutting means; a'first and second multiple power transmittingpath from said source of power to said knife cutting means; means fortransmitting power from said source of power to said knife cutting meansover said first path for operating said knife cutting means at aconstant speed; means including elliptical gears in said second path fortransmitting power from said source of power to said knife cutting meansfor accelerating said knife cutting means to a speed synchronous withthe speed of said strip material at the instant of cutting said stripmaterial and for decelerating/said knife cutting means to said constantspeed; means in said first path for varying said constant speed at whichthe knife cutting means is operated from said source of power; and meansfor alternately rendering said first and second multiple powertransmitting paths operative for each cycle of operation.

13. In a device for cutting strip material, knife cutting means; asource of power fo driving said strip material at a constant speed p stsaid knife cutting means; a first and second multiple power transmittingpath from said source of power to said knife cutting means; meansincluding a one way clutch mechanism for transmitting power from saidsource of power to said knife cutting means over said first path foroperating said knife cutting means at a constant speed; means includingelliptical gears and'a one way clutch mechanism in said second path fortransmitting power from said source of power to said knife cutting meansfor accelerating said knife cutting means to a speed synchronous withthe speed of said strip material at the instant of cutting said stripmaterial and for decelerating said knife cutting means to said constantspeed; means in said first path for varying said constant speed at whichI cutting means; a source of power; a first and second multiple powertransmitting path from said source of power to said knife cutting means;means for transmitting power from said source of power to said knifecutting means over said first path for operating said knife cuttingmeans at a constant speed; means in said second path for transmittingpower from said source of power to said knife cutting means foraccelerating and decelerating said knife cutting means from and to saidconstant speed; means in said first path for varying said constant speedat which the knife cutting means is operated from said source of power;and calibrated means for indicating the speed variations for eachpredetermined size of strip material to be cut.

15. In a device for cutting continuously advancing strip material, acyclically operable knife cutting means for periodically engaging saidstrip material for cutting; a source of power for operating said knifecutting means; means for vary.- ing the frequency of operation of saidknife cutting means for changing the sizes of strip mate-;

rial cut; and non-adjustable automatic means for invariably bringingsaid knife cutting means to synchronous speed with said strip materialduring the cutting operation for every size of strip material cut, saidmeans comprising a pair of elliptical gears.

16. In a device for cutting continuously advancing strip material, acyclically operable knife cutting means for periodically engaging saidstrip material for cutting; a source of power for operating said knifecutting means; means for varying the frequency of operation of saidknife cutting means from said source of power for varying the sizes ofstrip material out, said last mentioned means being operable only duringthe interval between cutting operations; and automatic means forcontrolling the speed of operation of said knife cutting during apredetermined portion of the cycle of operation including the cuttinginterval for invariably bringing said knife cutting means to synchronousspeed with said strip material during the cutting interval, said lastmentioned means being non-operative to control said knife cutting meansduring the remaining interval of the cycle.

17. In a device for cutting continuously advancing strip material, acyclically operable knife cutting means for periodically engaging saidstrip material for cutting; a source of power for operating said knifecutting means; means for varying the frequency of operation of saidknife cutting means from said source of power for varying the sizes ofstrip material out, said last mentioned means being operable only duringthe interval between cutting operations; and elliptical gear means forcontrolling the speed of operationof said knife cutting means during apredetermined portion of the cycle of operation including the cuttinginterval for invariably bringing said knife cutting means to synchronousspeed with said strip material during the cutting interval, said lastmentioned means being non-operative to control said knife cutting meansduring the remaining interval of the cycle.

18. In a device for cutting continuously advancing strip material, acyclically operable knife cutting means for periodically engaging saidstrip material for cutting; a source of power for operating said knifecutting means; means for varying the frequency of operation of saidknife cutting means for changing the sizes of strip material cut; andelliptical gear means for transmitting driving power to said knifecutting means to bring its speed to synchronous speed with said stripmaterial at an invariable predetermined rate, the cutting operationinvariably occurring at a predetermined position of said ellipticalgears irrespective of the variation in the frequency of the cuttingcycle.

19. In a device for cutting continuously advancing strip material,a'cyclically operable knife cutting means for periodically cutting saidstrip material; 'a source of power for operating said knife cuttingmeans; means for varying the frequency of operation of said knifecutting means for changing the sizes of strip material cut; and a speedchanging means for invariably bringing said knife cutting means to thesame speed as said strip material at the period of cutting for everyfrequency of operation of said knife cuttin means.

- 20. In a device for cutting continuously advancing strip material, acyclically-operable knife cutting means for periodically cutting saidstrip material; a source of power; means connecting said source of powerto said knife cutting means for driving said knife cutting means; meansfor varying the frequency of operation of said knife cutting means forchanging the sizes of strip material cut; and speed changing meansincluded in said first-mentioned means for invariably bringing saidknife cutting means to the same speed as said strip material at theperiod of cutting for every frequency of operation of said knife cuttingmeans.

21. In a device for cutting continuously advancing strip material, acyclically operable knife cutting means for periodically cutting saidstrip material; a ,source of power; means connecting said source ofpower to said knife cutting means for driving said knife cutting means;means for varying the frequency of operation of said knife cutting meansfor changing the sizes of strip ma,- terial cut; and speed changingmeans included in said first-mentioned means for invariably bringingsaid knife cutting means to the same speed as said strip material at theperiod of cutting for every frequency of operation of said knifecutting-means, the rate of speed change being different for eachfrequency of operation of said knife cutting means, whereby the knifecutting means is brought to the same speed at the cutting period for allsizes of strip material.

22. In a device for cutting continuously ad-, vancing strip material, acyclically operable knife cutting means for periodically cutting saidstrip material; a source of power; means connecting said source of powerto said knife cutting means for driving said knife cutting means; meansfor varying the frequency of operation of said knife cutting means forchanging the sizes of strip material cut; and speed changing meansincluded in said first-mentioned means for invariably bringing saidknife cutting means to a fixed pre-

